WO2001007176A1

WO2001007176A1 - Electromagnetic device and driver circuit

Info

Publication number: WO2001007176A1
Application number: PCT/JP2000/002346
Authority: WO
Inventors: Gunchu Iwasaki; Kenta Namioka
Original assignee: Iwasaki Seiki Corporation; M.T.I. Corporation
Priority date: 1999-07-27
Filing date: 2000-04-11
Publication date: 2001-02-01
Also published as: EP1116524A1; IL142143A0; CA2345547C; CN1319034A; TW443057B; JP3545650B2; RU2212954C2; KR100433050B1; JP2001029888A; MXPA01003154A; BR0006953A; MY125308A; US6597268B2; CA2345547A1; KR20010073194A; US20010028290A1; EP1116524A4; AU759287B2; AU3676600A; CN1161190C

Abstract

An electromagnetic device comprises a coil bobbin (1) supporting a magnetic coil (5), and a U-shaped moving iron (2) with one side (2a) sandwiched fixedly between a pair of cores (3, 4) in a hollow (1a) of the coil bobbin (1). The other side (2b) of the U-shaped moving iron (2) is inserted in a hole (1c) of the coil bobbin (1) and urged resiliently away from the side (2a). The cores (3, 4) are bent to form rising edges (3a, 4a) whose tops are opposed to the other side (2b) at a predetermined distance.

Description

Description Electromagnetic device and its driving circuit

The present invention relates to an electromagnetic device suitable for an extremely small vibration device, a switch device, and the like, and a drive circuit thereof.

Background art

In recent years, the spread of mobile phones has been remarkable, but the use of vibration notification for calls has been the mainstay for expanding the user base and convenience. This is because an eccentric weight is attached to the main shaft of a motor built in the telephone body, and the eccentric weight is rotated by the rotation of the motor which is started simultaneously with the reception of a call signal, and the phase difference between the axis and the eccentric is converted into vibration. The vibration is transmitted to the user.

Conventionally, a coreless motor is usually used for this kind of purpose (see, for example, Japanese Patent Application Laid-Open No. Hei 4-275046), which has a complicated structure and is expensive. Since the motor is used with the eccentric weight attached to the motor shaft, it cannot be rotated.Therefore, there is a problem in durability due to the loss of bearings and the deformation of the rotating shaft. Because of the necessity, a relatively large space was required for the vibration generator, and there was a problem in miniaturization. It was also disadvantageous in terms of effective use of electricity.

Further, there has been proposed a system in which a pulse motor is incorporated so that a vibration pattern can be selected so that an intended partner can be reliably called up when necessary (for example, see Japanese Patent Application Laid-Open No. H5-11-1). However, this method also had the same problem as described above.

Therefore, an object of the present invention is to provide an electromagnetic device suitable for a vibration device and the like which can be manufactured in a small size and at a low cost, can guarantee high operation reliability and durability, and can effectively use electric power. An object of the present invention is to provide a device and a driving circuit thereof.

Disclosure of the invention

An electromagnetic device according to the present invention includes: a coil bobbin for supporting an exciting coil; A U-shaped movable iron piece made of a soft magnet material having a resilient characteristic in which one side is fixed in the bin in the axial direction of the excitation coil and the other side is separated from the one side; The other side of the movable iron piece is piled up by its elastic force so as to be opposed to the end of the other side at a predetermined interval so as to face the end of the other side at a predetermined interval. I have.

In addition, the electromagnetic device according to the present invention has a coil bobbin that supports an exciting coil, and has a resilient characteristic in which one side of the coil bobbin is fixed in the axial direction of the exciting coil and the other side is separated from the one side. A U-shaped movable iron piece made of a soft magnetic material configured; a leaf spring having a base fixed to the other side and a tip extending beyond the tip of the other side; and the tip of the leaf spring. And the other side of the movable iron piece is resiliently moved by the coil pobin so that the end of the one side and the end of the other side of the movable iron piece face each other at a predetermined interval. It is restrained so that it can be displaced against the force.

In addition, the electromagnetic device according to the present invention may further include a coil bobbin that supports an exciting coil, a coil bobbin having one side inserted and fixed in the axial direction of the exciting coil, and the other side facing the one side at a predetermined interval. A U-shaped movable iron piece made of a soft magnet material formed; and the movable so as to have a characteristic that one side is fixed to the coil pobin in the axial direction of the exciting coil and the other side is separated from the one side. A U-shaped leaf spring formed along the iron piece, wherein the other side of the leaf spring is restrained by the coil pobin so as to be displaceable with the movable iron piece against its elastic force. .

In addition, the electromagnetic device according to the present invention may further include a coil bobbin that supports an exciting coil, a coil bobbin having one side inserted and fixed in the axial direction of the exciting coil, and the other side facing the one side at a predetermined interval. A U-shaped movable iron piece made of a soft magnetic material displaceably engaged with the coil pobin, and interposed between the opposing sides of the movable iron piece and pressed so as to separate the opposing sides. And ammunition members.

According to the present invention, at least one of the opposing sides of the movable iron piece is bent toward the other so as to increase the number of interlinkage magnetic fluxes. At least one of the opposing sides is fixed with a protruding iron piece so that the number of interlinkage magnetic fluxes increases toward the other side.

Further, according to the present invention, the movable bobbin is fixed to the coil bobbin in the axial direction of the exciting coil so as to be engaged with a tip of the one side of the movable iron piece and to be chained toward the other side of the movable iron piece. It further includes an iron core having an upright portion bent so as to increase the number of magnetic fluxes.

Further, according to the present invention, the movable iron piece is inserted and fixed to the coil bobbin so as to sandwich the one side of the movable iron piece in the axial direction of the exciting coil, and one of the movable iron pieces is engaged with a tip of the one side of the movable iron piece. A first upright portion bent so as to increase the number of interlinkage magnetic fluxes toward the other side of the movable iron piece, and the other of the movable iron piece adjacent to the first upright portion. It further includes a pair of iron cores having a second upright portion bent so as to increase the number of interlinkage magnetic fluxes toward the side.

According to the invention, the top surface of the upright portion is formed by bending the upright portion.

According to the present invention, the magnetic path length determined by the U-shaped movable iron piece and the iron core is 24 to 36 mm, and the cross-sectional area of the movable iron piece is 1.2 to 3.2 mm ² The cross-sectional area of the iron core is selected to be 2.4 to 3.6 mm ² .

Further, the drive circuit for the electromagnetic device according to the present invention is configured such that a serial circuit including a normally open switch closed by a ringing signal for a predetermined time, a power supply, and a current pulse circuit is connected in series to the excitation coil. It is constituted by doing.

Further, according to the present invention, an arithmetic unit is connected to the current pulse circuit, and the arithmetic unit allows the current pulse supplied to the excitation coil from the current pulse circuit to be energized for a period of time, a period of energization, and a duration of energization. At least one of them can be adjusted in less time.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a plan view of a first embodiment of the electromagnetic device according to the present invention.

2 is a side view of the first embodiment.

FIG. 3 is a bottom view of the first embodiment.

FIG. 4 is a central longitudinal sectional view of FIG. FIG. 5 is a sectional view taken along the line VV in FIG.

FIG. 6 is a left side view of FIG.

FIG. 2 is a circuit configuration diagram showing an example of a drive circuit used in the electromagnetic device according to the present invention.

FIG. 8 is a diagram showing current pulses supplied to the excitation coil.

FIG. 9 is a schematic configuration diagram of a first modification of the first embodiment.

FIG. 10 is a schematic configuration diagram of a second modification of the first embodiment.

FIG. 11 is a schematic configuration diagram of a third modification of the first embodiment.

FIG. 12 is a schematic configuration diagram of a second embodiment of the electromagnetic device according to the present invention.

FIG. 13 is a schematic configuration diagram of a first modification of the second embodiment.

FIG. 14 is a schematic configuration diagram of a second modification of the second embodiment.

FIG. 15 is a schematic configuration diagram of a third modification of the second embodiment.

FIG. 16 is a schematic configuration diagram of a third embodiment of the electromagnetic device according to the present invention.

FIG. 17 is a schematic configuration diagram of a first modification of the third embodiment.

FIG. 18 is a schematic configuration diagram of a second modification of the third embodiment.

FIG. 19 is a schematic configuration diagram of a third modification of the third embodiment.

FIG. 20 is a schematic configuration diagram of a fourth modification of the third embodiment.

FIG. 21 is a plan view of a fourth embodiment of the electromagnetic device according to the present invention.

FIG. 22 is a side view of the fourth embodiment.

FIG. 23 is a central longitudinal sectional view of the fourth embodiment.

FIG. 24 is a left side view of FIG.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the illustrated examples. 1 to 6 showing a first embodiment of an electromagnetic device according to the present invention, reference numeral 1 denotes a lipobin having a cavity 1a having both ends open, an exciting coil mounting portion 1b, and a through hole 1c, and 2 One side 2a is passed through the hollow portion 1a of the coil bobbin 1 and the other side 2b is passed through the through hole 1c of the coil bobbin 1 so that both sides are separated from each other so as to have a magnetic firing characteristic. The movable iron pieces 3 and 4 obtained by bending a strip made of a soft magnet material that has not been dulled into a U-shape. The movable iron pieces 3 and 4 are fixed through the cavity 1a of the coil bobbin 1 while holding the movable iron piece 2 therebetween. One end is bent so as to rise toward the other side 2 b of the movable iron piece 2, and the top face is bent by bending the tops of the rising parts 3 a and 4 a as shown in FIG. 5 is an exciting coil composed of an electric wire wound around the magnetic coil mounting portion 1b of the coil bobbin 1, and 6 is screwed onto the coil bobbin 1 to connect the exciting coil 5 to a power source. Connection terminal. In this case, the tip of one side 2a of the movable iron piece 2 and the base of the upright portion 3a of the iron core 3 are engaged as shown in FIG. 5, and the movable iron piece 2 and the iron core 3 are connected to the upright portion 3a. In addition, the other side 2b of the movable iron piece 2 is normally piled by its elasticity and is restrained by the upper wall of the through hole 1c of the coil bobbin 1. Thus, a predetermined distance from the common top surface of the upright portions 3a, 4a of the iron cores 3, 4 is maintained. When this electromagnetic device is used as a vibrating device for notifying the arrival of a call signal from a mobile phone or the like, a protrusion 2 b ′ is formed at the tip of the other side 2 b of the movable iron piece 2. Is done.

The block diagram in FIG. 7 shows a basic configuration of a drive circuit used in the present electromagnetic device. In the figure, 7 is a normally open switch that is closed for a predetermined time when the call signal S arrives, 8 is a power supply battery, 9 is a vibration mode selected by the arithmetic unit 10, that is, excitation of the electromagnetic device. energization time t of the current pulses supplied to the coil 5, a current pulse circuit configured so as to be able to adjust the one least the current period t ₂ and duration T (see FIG. 8). When the electromagnetic device is used as a vibrating device for notifying a call of a mobile phone, a CPU incorporated in the mobile phone can be used as the arithmetic device 10.

Since the first embodiment is configured as described above, its operation will be described by taking as an example a case where the switch is used as a vibrating device for notifying a call of a mobile phone. When the switch 7 is closed, the current pulse circuit 9 supplies the excitation coil 5 with a pulse current having the conduction time t, the conduction cycle t, and the conduction duration T set by the arithmetic unit 10. Thus, when the excitation coil 5 is energized, a magnetic flux is generated in the magnetic circuit composed of the movable iron piece 2 and the iron cores 3, 4, and the other side 2 b of the movable iron piece 2 and the iron cores 3, 4 Attraction force is generated in a direction to reduce the magnetic gap between the upright portions 3a and 4a, that is, in a direction against the resilience of the other piece 2b, and the other piece 2b of the movable iron piece 2 It is displaced as shown by the dashed line in Fig. 4. Thus, to exciting coil 5 When the energization of the magnetic circuit is cut off, the magnetic flux of the magnetic circuit disappears, and the magnetic circuit demagnetizes. As a result, the repulsive force of the other piece 2b of the movable iron piece 2 overcomes the attraction force of the magnetic circuit, and the other piece 2b contacts the upper wall of the through hole 1c of the coil bobbin 1 (see FIG. 4). At this time, the projection 2b 'hits the wall (not shown) of the mobile phone. Then, by energizing and interrupting the excitation coil 5, that is, repeating the above displacement of the other side 2 b of the movable iron piece 2, vibration is generated, and the user is notified of the arrival of the call signal.

In this case, the frequency is determined as follows: the period of time during which the pulse current is applied to the exciting coil 5, the “period” duration, the inductance of the exciting coil 5, the time constant of the drive circuit, the permeance of the magnetic flux gap, and the It is determined by the elastic force of the other side 2b, that is, the spring constant. Accordingly, this vibration can be appropriately modulated by making at least one of the “period” and “period” of the pulse current variable through the arithmetic unit 10 in practice. By utilizing this modulation action, it is possible to apply to the same other party to distinguish between a normal call and an emergency call and to notify them, and the call function can be further improved. In the present embodiment, the suction efficiency can be improved by increasing the number of interlinkage magnetic fluxes by using a plurality of iron cores and increasing the number of interlinkage magnetic fluxes by appropriately expanding the attraction portion of each iron core by bending the end of the iron core itself. In addition, an appropriate spring constant (elastic force) is applied to the other side 2 b of the U-shaped movable iron piece 2 which can be relatively long, and a part of the coil pobin 1 (the upper wall of the through-hole portion 1 c) is provided. ), So that the movement of the other side 2b can be restrained, it is easy to assemble and can be made compact, and it is strong for its size, and it is a vibration device that is strong in operation reliability and durable. Can be provided. Another advantage is that it can be used with a simple drive circuit.

9 to 11 show different modifications of the first embodiment. That is, in the modification shown in FIG. 9, the iron core 4 is omitted, and the top of the upright portion 3a, that is, the suction portion, bends the end portion of the iron core 3 doubly to enlarge the area of the suction portion and interlink. The feature is that the number of magnetic fluxes can be increased. In the modification of FIG. 10, the iron core is formed by bending the tip of the other side 2 b of the movable iron piece 2 toward the side 2 a while the iron core is also used as one side 2 a of the U-shaped movable iron piece 2. The modification of FIG. 11 is characterized in that the iron core is also used as one side 2 a of the U-shaped movable iron piece 2 and the suction part is the same as the movable iron piece 2. The chain is fixed to the tip of the other side 2 b by caulking or the like. It is characterized in that it is composed of iron pieces 11 formed so that the number of magnetic fluxes increases. All of these modifications are similar to those of the first embodiment except for the configuration other than the above, and the basic operation and effects are the same as those of the first embodiment. Therefore, detailed description is omitted, but the modifications of FIGS. 10 and 11 are particularly smaller. There is an advantage that it can be configured as follows. In the modification of FIG. 10, instead of bending the tip of the other side 2b of the U-shaped movable iron piece 2, the tip of one side 2a may be bent upward. In the modification of FIG. 11, the iron piece 11 may be fixed to one side 1 a of the U-shaped movable iron piece 2.

FIG. 12 shows a second embodiment of the present invention. In the figure, substantially the same members and portions as those of the first embodiment are denoted by the same reference numerals, and detailed description is omitted. In this embodiment, the U-shaped movable iron piece 2 is magnetically annealed, and the separating force of the other side 2 b with respect to one side 2 a is strong, and the one side 12 a is formed in the hollow portion 1 a of the coil bobbin 1 by the U-shaped movable iron piece 2. Is formed along the movable iron piece 2 so as to have an elastic characteristic in which the one side 2a and the iron cores 3 and 4 are inserted and fixed together and the other side 12b is separated from the one side 12a. The first embodiment is configured such that 1 2 b ′ is provided by a U-shaped leaf spring 12 which is engaged with the other side 2 b of the movable iron piece 2 by an appropriate known method. Different from the example. Since the operation and effect of this embodiment are the same as those of the first embodiment, description thereof will be omitted.

FIGS. 13 to 15 show different modifications of the second embodiment. That is, in the modification shown in FIG. 13, the iron core 4 is omitted, and the top of the upright portion 3 a, that is, the suction portion, bends the end portion of the iron core 3 doubly to enlarge the area of the suction portion and to reduce the chain. It has a feature in that the number of alternating magnetic fluxes is increased. In the modified example of Fig. 14, the iron core is also used as one side 2a of the U-shaped movable iron piece 2 and the suction portion is bent in two steps with the tip of the other side 2b of the movable iron piece 2 directed to one side 2a. It is characterized in that it is formed so as to increase the number of interlinkage magnetic fluxes, thereby simplifying the configuration.The modification of FIG. 15 is such that the iron core is a side 2 a of the U-shaped movable iron piece 2. And the suction part is fixed to the tip of the other side 2b of the movable iron piece 2 and the tip of the other side 12b of the U-shaped leaf spring 12 in common by force crimping or the like. It is characterized in that it is composed of 1 1. In each of these modified examples, the configuration other than the above and the basic operation and effect are the same as those of the second embodiment, and therefore detailed description is omitted. In the modification of FIG. 14, instead of bending the tip of the other side 2 b of the U-shaped movable iron piece 2 into two steps, the tip of one side 2 a is turned upward in the same manner. You may make it bend | fold. Further, in the modified example of FIG. 15, the iron piece 11 may be fixed to one side 2 a of the U-shaped movable iron piece 2 and one side 12 a of the U-shaped leaf spring 12 in common.

FIG. 16 shows a third embodiment of the present invention. In the drawing, members and portions substantially the same as those in the above-described embodiment are denoted by the same reference numerals, and detailed description is omitted. In this embodiment, the U-shaped movable iron piece 2 is magnetically annealed, and the separation force between the side 2a and the other side 2b is interposed therebetween. It differs from any of the previously described embodiments in that it is configured to be provided by a coil spring 13 loosely wound on a and 4a. This embodiment is the same as the first embodiment except for the feature that the assembly of the device is relatively simple, and therefore the description is omitted.

FIGS. 17 to 20 show different modifications of the third embodiment. That is, in the modification shown in FIG. 17, the iron core 4 is omitted, and the top of the upright portion 3 a, that is, the suction portion, bends the end of the iron core 3 doubly to enlarge the area of the suction portion, thereby reducing the chain length. It has a special feature in that the number of alternating magnetic fluxes can be increased. The modification of FIG. 18 is such that the iron core is also used as one side 2 a of the U-shaped movable iron piece 2, and the suction portion can increase the number of interlinkage magnetic fluxes at the tip of the other side 2 b of the movable iron piece 2. It is formed by being bent in two steps toward one side 2a, and is characterized by the fact that the coil spring 13 is wound around this bent portion to further simplify the configuration. Is composed of an iron piece 11 whose iron core is also used as one side 2a of the U-shaped movable iron piece 2 and whose suction portion is fixed to the tip of the other side 2b of the movable iron piece 2 by a method such as force crimping. However, it is characterized in that a coil spring 13 is wound around this iron piece 11. In the modification of FIG. 20, the iron piece 11 is fixed to the tip of one side 2 a of the U-shaped movable iron piece 2 by caulking or the like so as to face the iron piece 11. It differs from the modified example of FIG. 19 in that a coil spring 13 is wound around 1 and 11 in common. In each of these modifications, the configuration other than the above and the basic operation and effects are the same as those of the third embodiment, and thus detailed description is omitted. The coil spring 13 is an example of an elastic member, and is not limited to this. In the modified example of FIG. 18, instead of bending the tip of the other side 2 b of the U-shaped movable iron piece 2 in two steps, the tip of one side 2 a is bent upward in the same manner. Moyo No. Further, in the modified example of FIG. 19, the iron piece 11 may be fixed to one side 2 a of the U-shaped movable iron piece 2.

FIGS. 21 to 24 show a fourth embodiment of the present invention. In the drawing, members and portions that are substantially the same as those in the above-described embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. This embodiment has a side 14a and another piece 14b along the U-shaped movable iron piece 2 configured in the same manner as the first embodiment except for the protrusion 2b '. The base of b may be fixed to the other side 2b of the U-shaped movable iron piece 2 by caulking or the like, and the tip may extend beyond the tip of the other side 2b, and a weight 15 may be attached to the tip. It differs from any of the above-described embodiments in that a thin U-shaped leaf spring 14 having a high flexibility is provided. In this embodiment, when the other side 2b of the U-shaped movable iron piece 2 is moved by suction and resilience, inertia due to the weight 15 is added, and the other end 14b of the U-shaped leaf spring 14 front end portion 14b This is extremely effective when it is used for a vibrating device or the like to notify the call of a mobile phone, especially because the displacement amount at the time of the bombing increases.

As is clear from the above description, as a material of the U-shaped movable iron piece 2 and the iron cores 3 and 4, an electromagnetic pure steel plate or a permalloy plate is used. According to the experiment of the applicant of the present application, the U-shaped movable iron piece 2 and the iron cores 3 and 4 are used in consideration of power consumption, vibration excitation force, saturation magnetic flux density, elasticity, and the like. The formed magnetic path length is 24 to 36 mm, the cross-sectional area of the movable iron piece 2 is 1.2 to 3.2 mm ² , and the cross-sectional area of the iron cores 3 and 4 is 2.4 to 3.6 mm ² The result that the range is optimal was obtained.

In the above embodiment, the description has been made on the assumption that the present electromagnetic device is applied to a vibrating device for a cellular phone. However, the present electromagnetic device may be used as a notification device for electromagnetic switchgear or other communication devices, or an electromagnetic drive application device. In particular, it is possible to construct a powerful vibration device even with a very small size and to prevent the vibration of the vibration part from propagating to the device body. Or, it can be used in a headphone or headphone style by holding it around the ear, and various other uses are possible.

Industrial applicability

As described above, the electromagnetic device of the present invention is practically useful because its structure and assembly are simple and easy to incorporate into equipment.

Claims

The scope of the claims

1. A coil bobbin for supporting an exciting coil, and a soft magnet material configured to have a resilient characteristic in which one side is fixed to the coil bobbin in the axial direction of the exciting coil and the other side is separated from the one side. And the other side of the movable iron piece is moved by the coil pobin so that the end of the one side of the movable iron piece and the end of the other side face each other at a predetermined interval. An electromagnetic device that is restrained so that it can be displaced by being piled on its elastic force.

2. A leaf spring having a base fixed to the other side and a tip extending beyond the tip of the other side, and a weight fixed to the tip of the leaf spring. An electromagnetic device according to claim 1.

3. A coil bobbin for supporting an exciting coil, and a soft magnet material formed such that one side is inserted through and fixed to the coil bobbin in the axial direction of the exciting coil, and the other side is opposed to the one side at a predetermined interval. A U-shaped movable iron piece, and a U-shape formed along the movable iron piece such that one side is inserted and fixed to the coil bobbin in the axial direction of the exciting coil and the other side is separated from the one side. An electromagnetic device comprising: a leaf spring; wherein the other side of the leaf spring is suppressed by the coil bobbin so as to be displaceable together with the movable iron piece against its resilient force.

4. A coil bobbin that supports an exciting coil, and is displaceably displaceable to the coil bobbin such that one side is fixed to the coil bobbin in the axial direction of the exciting coil and the other side faces the one side at a predetermined interval. An electromagnetic device comprising: a U-shaped movable iron piece made of a combined soft magnetic material; and a resilient member interposed between the opposed sides of the movable iron piece and elastically pressed to separate the opposed sides. apparatus.

5. The electromagnetic device according to claim 1, wherein at least one of the opposing sides of the movable iron piece is bent toward the other so as to increase the number of interlinkage magnetic fluxes.

6. An iron piece formed and protruded toward at least one of the opposing sides of the movable iron piece so as to increase the number of flux linkages toward the other, and is fixed to at least one of the opposite sides. An electromagnetic device according to claim 1.

7. The coil coil is fixed to the coil pobbin in the axial direction of the exciting coil so as to engage with the tip of the one side of the movable iron piece and increase the number of magnetic flux linkages toward the other side of the movable iron piece. 5. The electromagnetic device according to claim 1, further comprising an iron core having an upright bent portion.

8. The coil bobbin is fixed so as to sandwich the one side of the movable iron piece in the axial direction of the exciting coil, one of which is engaged with the tip of the one side of the movable iron piece and the other of the movable iron piece. A first upright portion bent so as to increase the number of interlinkage magnetic fluxes toward the other side, and the other to the other side of the movable iron piece adjacent to the first upright portion; 5. The electromagnetic device according to claim 1, further comprising a pair of iron cores having a second upright portion bent so as to increase the number of interlinkage magnetic fluxes.

9. The electromagnetic device according to claim 7, wherein a top surface of the upright portion is formed by bending the upright portion.

10. The magnetic path length determined by the U-shaped movable iron piece and the iron core is 24 to 36 mm, the cross-sectional area of the movable iron piece is 1.2 to 3.2 mm ² , area from 2.4 to 3. electromagnetic device according to claim 1, which is respectively selected to be 6 mm ^2.

11. The electromagnetic circuit according to claim 1, wherein a series circuit including a normally open switch, a power supply and a current pulse circuit, which is closed for a predetermined time in response to an incoming call signal, is connected to the excitation coil in series. Circuit for driving the device.

12. An arithmetic unit is connected to the current pulse circuit, and the arithmetic unit uses at least one of a conduction time, a conduction cycle, and a duration of a current pulse supplied to the excitation coil from the current pulse circuit. 21. The circuit according to claim 11, wherein the circuit can be adjusted.